WA property tycoon Nigel Satterley has vowed to defend legal action against the Satterley Property Group by a group of Secret Harbour families who claim the company mislead them over the location of the Mandurah road and rail.

The group of nine families lodged their writs in the Federal Court this morning claiming they were the victims of a breach of the Federal Trade Practices Act and a breach of contract.

The families claim they were not told about the realignment of the Mandurah road when they purchased their blocks.

They claim the omission resulted in the busy road being metres from their doorsteps, and that they were misled about the close proximity of the Mandurah railway.

The residents are being represented by high-profile lawyer John Hammond.

Mr Satterley said the allegations against Satterley Property Group would be strongly defended.